The sum of a brother's and sister's ages is 57 years. If the brother is 5 years older than his sister, find their ages.

We can make formulas for this.

Assume x=male age and y=female age.

From this problem, we know that x+y=57 and x-5=y since the brother is older. We can do substitution and plug in the second formula into the first.

x+(x-5)=57

2x-5=57     Add like terms (x)

2x=62         Isolate

x=31

Then plug this into the original to find out y.

x+y=57

31+y=57

y=26

use this formula:

p(a\b) = p(a and b)/p(b).

take it from here.